Displacement sensor

ABSTRACT

A displacement sensor includes a plurality of conductive members, a semiconductor device, and a nonmagnetic conductor electrically connecting one of the conductive members and one of a low electric potential side and a high electric potential side of a power supply of the semiconductor device. The conductive member is electrically connected with the semiconductor device through a nonmagnetic conductor.

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 10/953,531 filed Sep. 30, 2004.

BACKGROUND OF THE INVENTION

The present invention relates to a displacement sensor sensing arotation angle of a rotary member, and more specifically to adisplacement sensor sensing a throttle valve opening and an acceleratorpedal opening of a vehicular engine.

U.S. Pat. No. 5,798,639 (corresponding to Published Japanese PatentApplication Kokai No. H07(1995)-260412) shows a rotation angle sensorincluding a magnetic circuit and an electric circuit. The magneticcircuit is composed of a magnet provided in a rotary shaft rotating inaccordance with a throttle valve opening, and yokes surrounding themagnet nearly over the full circumference. The electric circuit includesa magnetoelectric transducing element, such as a Hall effect device,disposed between the yokes, and a signal processing circuit.

The Hall effect device senses magnetic flux density varying inaccordance with the rotation angle, in the magnetic circuit, and thesignal processing circuit determines the rotation angle by processing asignal from the Hall effect device.

SUMMARY OF THE INVENTION

In this rotation angle sensor, the magnetic circuit of the yokes and theelectric circuit of the magnetoelectric transducing element are isolatedelectrically by a structure retaining member made of nonmagneticmaterial such as high-polymer resin. In this arrangement, the magneticcircuit is not held equal in electric potential with respect to theelectric circuit.

Therefore, an electric potential difference is generated in the magneticcircuit by electric charges stored in the magnetic circuit. Thiselectric potential difference may cause electron generation or variationin positive hole density in the magnetoelectric transducing element andthe signal processing circuit in the electric circuit. Consequently,operations of magnetoelectric transducing element and the signalprocessing circuit are changed, and the characteristic of the device ischanged.

When, for example, electrons are induced in an N-type semiconductorregion by this electric potential difference, the resistance of theN-type semiconductor region decreases. When electrons are induced in aP-type semiconductor region by this electric potential difference, theresistance of the P-type semiconductor region increases. In some cases,an inversion layer may be generated.

It is an object of the present invention to provide a displacementsensor which suppresses a change of the output characteristic, andenhances reliability.

According to one aspect of the present invention, a displacement sensorcomprises: a plurality of conductive members; a semiconductor device;and a nonmagnetic conductor electrically connecting one of theconductive members and one of a low electric potential side and a highelectric potential side of a power supply of the semiconductor device.

According to another aspect of the present invention, a displacementsensor comprises: a plurality of conductive members; a magnet disposedamong the conductive members; a magnetic sensing device to sense adisplacement of the magnet; and a nonmagnetic conductor electricallyconnecting one of the conductive members and one of a low electricpotential side and a high electric potential side of a power supply ofthe magnetic sensing device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic views showing two different examples of adisplacement sensor according to a first embodiment of the presentinvention.

FIG. 2 is a perspective view showing the displacement sensor of FIG. 1

FIG. 3 is a plan view showing the displacement sensor shown in FIG. 2.

FIG. 4 is a sectional view taken along a section line F4-F4 of FIG. 2.

FIG. 5 is a perspective view showing a displacement sensor according toa second embodiment of the present invention.

FIG. 6 is a plan view showing the displacement sensor shown in FIG. 5

FIG. 7 is a sectional view taken along a section line F7-F7 of FIG. 5.

FIG. 8 is a perspective view showing a displacement sensor according toa third embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1A and 1B show a displacement sensor according to a first orsecond embodiment of the present invention. This displacement sensorincludes a Hall effect device 11 as a magnetoelectric transducingelement or magnetic sensing device, and a yoke structure including yokes12 and 13 for introducing magnetic flux generated by a magnet (not shownin FIGS. 1A and 1B) into the Hall effect device 11 disposed, between theyokes 12 and 13. The Hall effect device 11 is connected with a lowelectric potential side of power supply 101, as shown in FIG. 1A.Alternatively, the Hall effect device 11 is connected with a highelectric potential side of power supply 102, as shown in FIG. 1B. Theyokes 12 and 13 are connected to the low or high electric potential sideof power supply 101 or 102 by a conductor 14 including at least oneportion made of nonmagnetic conductive material such as copper oraluminum. Therefore, the Hall effect device 11 and each yoke 12 or 13are electrically short-circuited, so that a electric potentialdifference therebetween is eliminated. At the same time the Hall effectdevice 11 and the yokes 12 and 13 are isolated magnetically.

The Hall effect device 11 is mounted on a lead frame 15, andelectrically connected to the lead frame 15 by wire bonding 16. The Halleffect device 11 is molded in a resin package 17.

FIGS. 2-4 show more in detail the connection between a yoke structureand a low or high electric potential side of power supply by anonmagnetic conductor according to the first embodiment. Thisdisplacement sensor shown in FIGS. 2-4 is composed of a magnet 20, ayoke structure including a pair of yokes 21 and 22, a Hall effect device23 serving as a magnetic sensing device, and a printed circuit board 25.

The magnet 20 is in the form of a rectangle or a oval shape (or a shapeof a racetrack). The magnet 20 extends from one end to the other in thelengthwise direction, and has magnetic poles in both ends, respectively.The magnet 20 produces magnetic flux to be sensed by the Hall effectdevice 23.

The yoke structure forms the magnetic circuit with the magnet 20. Theyoke 21 is made of magnetic material such as pure iron (SUYB, SUYP) orFe—Ni alloy, and arranged to conduct the magnetic flux generated by themagnet 20 to the Hall effect device 23, as described later. The yoke 21of this example includes a first pole piece portion 21A and a firstoverhang portion 21B. The first pole piece portion 21A is in the form ofan arcuate plate. The first pole piece portion 21A confronts the magnet20 radially across a predetermined constant radial gap. The firstoverhang portion 21B is in the form of a flat plate, and extendsradially inwardly from the first pole piece portion 21A over the magnet20. The first overhang portion 21B covers a part of the magnet 20 fromabove, and projects beyond the axis of the magnet 20. The first overhangportion 21B confronts the magnet 20 axially across a predeterminedconstant axial gap in the direction of the axis of the magnet 20.

The yoke 22 is made of the magnetic material like the yoke 21, locatedat a position diametrically opposite to the position of the yoke 21 toform the magnetic circuit, and arranged to conduct the magnetic fluxgenerated by the magnet 20 to the Hall effect device 23, as describedlater. Like the yoke 21, the yoke 22 includes a second pole pieceportion 22A and a second overhang portion 22B. The second pole pieceportion 22A is in the form of an arcuate plate. The second pole pieceportion 22A confronts the magnet 20 radially across a predeterminedconstant radial gap. The second overhang portion 22B in the form of aflat plate extends radially inwardly from the second pole piece portion22A across the axis of the magnet 20. The second overhang portion 22Bconfronts the magnet 20 axially at a predetermined constant axial gap inthe direction of the axis of the magnet 20.

The second pole piece portion 22A confronts the first pole piece portion21A diametrically across the magnet 20. Each of the first and secondpole piece portions 21A and 22A is curved in the form of a circular archaving a predetermined radius of curvature with respect to the rotationaxis of the magnet 20. Each pole piece portion 21A or 22A extendscircumferentially around the axis of the magnet 20 through asubstantially equal angle. In a cross section, each of the first andsecond pole piece portions 21A and 21B is in the form of a circular arc,and the angle subtended at the center by the arc of the second polepiece portion 22A is substantially equal to that of the first pole pieceportion 21A.

The second overhang portion 22B extends radially inwardly from the upperend of the second pole piece portion 22A, like the first overhangportion 21B, beyond the position of the axis of the magnet 20, andoverlaps the first overhang portion 21B across a predetermined axial gap26. The Hall effect device 23 is disposed axially between the first andsecond overhang portions 21B and 22B, as best shown in FIG. 4.

The Hall effect device 23 is a component of an internal electriccircuit. The Hall effect device 23 is mounted on a printed circuit board25, and disposed within the axial gap 26 between the first overhangportion 21B below and the second overhang portion 22B above. The Halleffect device 23 senses the magnetic flux in a direction parallel to therotation axis of the magnet 20, and perpendicular to the magnetizingdirection of the magnet 20. The Hall effect device 23 outputs a sensorsignal proportional to the magnetic flux density in the magnetic circuitcomposed of the magnet 20, and the yokes 21 and 22. The Hall effectdevice 23 is connected to a signal processing circuit (not shown). Thesignal processing circuit processes the sensor signal indicative of themagnetic flux density introduced by the yokes 21 and 22, and therebydetermines the rotation angle.

The printed circuit board 25 supports the Hall effect device 23 at theposition between the yokes 21 and 22, as mentioned above. Moreover, thesignal processing circuit (not shown) is formed on or in the printedcircuit board. The board 25 is formed with a slot passing through theboard 25. The slot is curved in conformity with the curvature of thesecond pole piece portion 22A of the yoke 22, and arranged to receivethe pole piece portion 22A. The second pole piece portion 22A passesthrough the slot of the board 25. The second pole piece portion 22A ofthe yoke 22 is fit in the slot so as to pass through the board 25.

A conductive pattern 27 is formed on the printed circuit board 25. Inthis example, the conductive pattern 27 includes an upper portion formedon a surface of the board 25, and an inner portion formed within theslot, on inner side wall surfaces defining the slot. The upper portionof the conductive pattern 27 of this example is formed on the uppersurface of the board 25, in a region fringing the slot. A conductivepattern 28 is formed on the lower surface or back surface of the board25. The conductive pattern 28 is similar in the surface shape to thefirst overhang portion 21B, as shown in FIGS. 2 and 3. The conductivepattern 28 confronts the upper surface of the first overhang portion21B.

The conductive patterns 27 and 28 are made of a nonmagnetic conductivematerial such as copper or aluminum. The conductive pattern 27 iselectrically connected to the second pole piece portion 22A of the yoke22 inserted through the slot of the board 25 by, for example, one ofwelding, clamping, soldering, wire bonding, and nonmagnetic conductiveadhesive. The conductive pattern 27 is connected to a wiring orinterconnection pattern (not shown) formed on the upper surface of theprinted circuit board 25. The conductive pattern 27 is connected,through the wiring pattern, with the low electric potential side ofpower supply 101 or the high electric potential side of power supply 102of the Hall effect device 23. Therefore, the yoke 22 is electricallyconnected, through the conductive pattern 27 and the wiring pattern, tothe low or high electric potential side of power supply 101 or 102 ofthe Hall effect device 23.

The conductive pattern 28 is electrically connected through a throughhole 29 formed in the printed circuit board 25, to the wiring pattern onthe upper surface of the board 25, by, for example, one of welding,clamping, soldering, wire bonding, and nonmagnetic conductive adhesive.The through hole 29 extends through the board 25 from the lower surfaceto the upper surface of the board 25. The wiring pattern is connected tothe low or high electric potential side of power supply 101 or 102connected with the Hall effect device 23. Therefore, the yoke 21 iselectrically connected, through the conductive pattern 28 and the wiringpattern, to the low or high electric potential side of power supply 101or 102 of the Hall effect device 23.

The yokes 21 and 22 are connected to the identical electric potential ofpower supply connected to the Hall effect device 23. Therefore, when theyoke 21 is connected to the low electric potential side of power supply101, the yoke 22 is also connected to the low electric potential side ofpower supply 101. When the yoke 21 is connected to the high electricpotential side of power supply 102, the yoke 22 is also connected to thehigh electric potential side of power supply 102. Moreover, the signalprocessing circuit is connected to the low or high electric potentialside of power supply 101 or 102 of the Hall effect device 23.

In this arrangement, the yokes 21 and 22 guides the magnetic fluxgenerated by the magnet 20, to the Hall effect device 23. The Halleffect device 23 generates the sensor signal indicative of the magneticflux density introduced into the Hall effect device 23. The sensorsignal is proportional to the magnetic flux density. This displacementsensor can determine the rotation angle of the magnet 20, i.e., therotation angle of the rotary shaft rotating as unit with the magnet, byprocessing the sensor signal.

As described above, according to the first embodiment, the magneticcircuit of the yokes 21 and 22 is connected, by the nonmagneticconductor (14, 27, 28), with the low or high electric potential side ofpower supply 101 or 102 of the electric circuit including the Halleffect device 23. Therefore, the arrangement of the nonmagneticconductor can act to eliminate an electric potential difference betweenthe magnetic circuit and the electric circuit, and at the same timeisolates the yokes and the magnetic sensing device magnetically.Therefore, this arrangement can protect the magnetoelectric transducingelement from electrostatic destruction, and prevent resistance changeand characteristic change of a semiconductor device due to electrongeneration or variation in positive hole density in the electriccircuit.

The nonmagnetic conductor connects the magnetic circuit and the electriccircuit by using one of welding, clamping, soldering, wire bonding, andnonmagnetic conductive adhesive. Therefore, this displacement sensor canensure both the proper operation of the magnetic circuit and theelectrical connection, without incurring magnetic interference.

The magnetoelectric transducing element can be electrically shielded bythe magnetic circuit connected to a fixed electric potential. Therefore,this displacement sensor can prevent the accuracy in the measurementfrom being lowered by external electric field.

FIGS. 5-7 show a displacement sensor according to a second embodiment ofthe present invention. In the second embodiment, a printed circuit board(PC board) 51 supporting the Hall effect device 13 has an arcuate endwhich abuts on the curved surface of the second pole piece portion 22Aof the yoke 22 with the interposition of a conductive pattern 52 of anonmagnetic conductive material such as copper or aluminum. The arcuateend of the board 51 is formed in an arcuate shape fitting to the arcuatesecond pole piece portion 22A. The conductive pattern 52 is formed onthe end face of the arcuate end of the board 51. The conductive pattern52 is electrically connected with the second pole piece portion 22A byone of welding, clamping, soldering, wire bonding, and nonmagneticconductive adhesive. In the other points, the displacement sensor of thesecond embodiment is substantially identical to the sensor according tothe first embodiment. The conductive pattern 52 is electricallyconnected to the wiring pattern formed on the surface of the board 51,like the conductive patterns 27 and 28. The wiring pattern is connectedwith the low or high electric potential side of power supply 101 or 102connected with the Hall effect device 23. Therefore, the conductivepattern 52 is electrically connected to the low or high electricpotential side of power supply connected to the Hall effect device 23.The conductive pattern 52 may include a first portion formed on theupper surface of the board 25 and a second portion formed on the endface of the board 25, like the conductive pattern 27.

The yokes 21 and 22 may be connected with the Hall effect device 23 bythe nonmagnetic conductor printed directly on a structural member, suchas a circuit board, of the electric circuit or the magnetic circuit. Itis possible to reduce a electric potential difference between the yokes21 and 22, and the electric circuit, by taking a low electric potentialside of power supply or a high electric potential side of power supplyfrom a signal processing circuit arranged to take power from a generator(not shown) or a storage battery (not shown) connected with the yokes 21and 22. The number of Hall effect devices is not limited to one. Therotational angle sensor may includes two or more Hall effect devices.

In the arrangement according to the first and second embodiments, thesensor is the displacement sensor configured to sense the rotation anglein accordance with the rotation of magnet 20. In the arrangementaccording to a third embodiment, a sensor is a linear displacementsensor configured to sense linear displacement of the magnet.

FIG. 8 shows a displacement sensor according to a third embodiment ofthe present invention. This displacement sensor includes yokes 81 a and81 b, a magnet 82, a Hall effect device 83, and a common yoke 84. Magnet82, yokes 81 a and 81 b, and Hall effect device 83 perform in the samemanner as magnet 20, yokes 21 and 22, and Hall effect device 23 shown inFIG. 2, respectively. Magnet 82 is disposed in an isolated space betweenyokes 81 a and 81 b confronting each other, and in an isolated spacebetween confronting surfaces of U-shaped common yoke 84. Hall effectdevice 83 is disposed adjacent to magnet 82, and disposed in theisolated space between yokes 81 a and 81 b confronting each other.Magnet 82 generates magnetic flux between yokes 81 a and 81 b andbetween the confronting surfaces of common yoke 84.

Yokes 81 a and 81 b between which Magnet 82 and Hall effect device 83are disposed are electrically connected through the nonmagneticconductor with a low electric potential side or a high electricpotential side of a power supply of the Hall effect device 83, by anonmagnetic conductor (not shown) like the first and second embodiments.

In the above-described arrangement, when magnet 82 is displaced in adirection shown by an arrow A of FIG. 8, the magnetic flux applied toHall effect device 83 is varied in accordance with variation in theconfronting areas between magnet 82 and each of yokes 81 a and 81 b. Thelinear displacement of magnet 82 is determined by sensing variation inthe magnetic flux density by Hall effect device 83. Similarly, whenmagnet 82 is displaced in a direction shown by an arrow B of FIG. 8, themagnetic flux applied to Hall effect device 83 is varied in accordancewith variation in the confronting areas between magnet 82 and each ofyokes 81 a and 81 b. The linear displacement of magnet 82 is determinedby sensing this variation in the magnetic flux by Hall element 83. Inthis arrangement according to third embodiment, the displacement sensoris provided with common yoke 84, and however it is possible to performin the same manner without providing with common yoke 84.

In this arrangement according to third embodiment, the nonmagneticconductor electrically connects yokes 81 a and 81 b with the lowelectric potential side of power supply 101 or the high electricpotential side of power supply 102 of the Hall effect device 23, andthereby this arrangement can prevent magnetic interference andgeneration of potential difference between yokes 81 a and 81 b.Moreover, it is possible to prevent characteristic change of thesemiconductor device due to electron generation, and to achieve the sameeffect as the first and second embodiments.

The nonmagnetic conductor is the conductive pattern printed on the boardon which the semiconductor device is mounted. The conductive patternincludes a first conductive pattern formed on the surface of the board,and a second conductive pattern formed on the side face of the board.Accordingly, it is possible to connect the conductor (conductive member)and the semiconductor device readily electrically.

The magnetic sensing device is a magnetoresistive element. Accordingly,it is possible to form the magnetic sensing device readily, and tominiaturize the magnetic sensing device.

The magnetic sensing device is a Hall element or a Hall IC. Accordingly,it is possible to form the magnetic sensing device readily, and tominiaturize the magnetic sensing device.

The nonmagnetic conductor is electrically connected to at least one ofthe semiconductor device and the magnetic sensing device by one ofwelding, clamping, soldering, wire bonding, and nonmagnetic conductiveadhesive. Accordingly, it is possible to connect the nonmagneticconductor with the conductor (conductive member), the semiconductordevice or the magnetic sensing device readily.

The nonmagnetic conductor is printed directly on at least one of theconductor, the semiconductor device, and the magnetic sensing device.Accordingly, it is possible to electrically connect the conductor withthe semiconductor device or the magnetic sensing device readily.

The magnetic sensing device is the semiconductor device. Accordingly, itis possible to form the magnetic sensing device readily, and tominiaturize the magnetic sensing device.

This application is based on a prior Japanese Patent Application No.2003-421036 filed on Dec. 18, 2003, and a prior Japanese PatentApplication No. 2004-364920 filed on Dec. 16, 2004. The entire contentsof these Japanese Patent Applications No. 2003-421036 and No.2004-364920 are hereby incorporated by reference.

Although the invention has been described above by reference to certainembodiments of the invention, the invention is not limited to theembodiments described above. Modifications and variations of theembodiments described above will occur to those skilled in the art inlight of the above teachings. The scope of the invention is defined withreference to the following claims.

1. A displacement sensor comprising: a plurality of conductive members;a semiconductor device; and a nonmagnetic conductor electricallyconnecting the semiconductor device and one of the conductive members incommon to one of a low electric potential side and a high electricpotential side of a power supply of the semiconductor device.
 2. Thedisplacement sensor as claimed in claim 1, wherein the displacementsensor further comprises a board supporting the semiconductor device;and the nonmagnetic conductor includes a conductive pattern formed onthe board.
 3. The displacement sensor as claimed in claim 2, wherein theconductive pattern of the nonmagnetic conductor is a pattern printed onthe board.
 4. The displacement sensor as claimed in claim 3, wherein theconductive pattern is a first conductive pattern; and the nonmagneticconductor further includes a second conductive pattern formed on theboard.
 5. The displacement sensor as claimed in claim 4, wherein thefirst conductive pattern of the nonmagnetic conductor is a patternformed on a surface of the board, and the second conductive pattern is apattern formed on a side face of the board.
 6. The displacement sensoras claimed in claim 1, wherein the nonmagnetic conductor is connected toat least one of the conductive members and the board by one of welding,clamping, soldering, wire bonding, and nonmagnetic conductive adhesive.7. The displacement sensor as claimed in claim 1, wherein thenonmagnetic conductor is printed directly on one of the conductivemembers and the semiconductor device.
 8. The displacement sensor asclaimed in claim 1, wherein the displacement sensor further comprises aplurality of nonmagnetic conductors each electrically connecting one ofthe conductive members and one of the low electric potential side andthe high electric potential side of the power supply of thesemiconductor device.
 9. The displacement sensor as claimed in claim 1,wherein at least one of said conductive members is magnetic, and whereinsaid nonmagnetic conductor is ungrounded.
 10. A displacement sensorcomprising: a plurality of conductive members; a magnet disposed amongthe conductive members; a magnetic sensing device to sense adisplacement of the magnet; and a nonmagnetic conductor electricallyconnecting the magnetic sensing device and one of the conductive membersin common to one of a low electric potential side and a high electricpotential side of a power supply of the magnetic sensing device.
 11. Thedisplacement sensor as claimed in claim 10, wherein the displacementsensor further comprises a board supporting the magnetic sensing device;and the nonmagnetic conductor includes a conductive pattern formed onthe board.
 12. The displacement sensor as claimed in claim 11, whereinthe conductive pattern of the nonmagnetic conductor is a pattern printedon the board.
 13. The displacement sensor as claimed in claim 12,wherein the conductive pattern is a first conductive pattern; and thenonmagnetic conductor further includes a second conductive patternformed on the board.
 14. The displacement sensor as claimed in claim 13,wherein the first conductive pattern of the nonmagnetic conductor is apattern formed on a surface of the board, and the second conductivepattern is a pattern formed on a side face of the board.
 15. Thedisplacement sensor as claimed in claim 14, wherein the nonmagneticconductor is connected to at least one of the conductive members and theboard by one of welding, clamping, soldering, wire bonding, andnonmagnetic conductive adhesive.
 16. The displacement sensor as claimedin claim 10, wherein the nonmagnetic conductor is printed directly onone of the conductive members and the magnetic sensing device.
 17. Thedisplacement sensor as claimed in claim 10, wherein the magnetic sensingdevice is a magnetoresistive element.
 18. The displacement sensor asclaimed in claim 10, wherein the magnetic sensing device is one of aHall element and a Hall IC.
 19. The displacement sensor as claimed inclaim 10, wherein the magnetic sensing device is a semiconductor device.20. The displacement sensor as claimed in claim 10, wherein thedisplacement sensor further comprises a plurality of nonmagneticconductors each electrically connecting one of the conductive membersand one of the low electric potential side and the high electricpotential side of the power supply of the semiconductor device.
 21. Adisplacement sensor comprising: a plurality of conductive magnetic-polemembers; a semiconductor device including a magnetic sensing device todetect a magnetic field between the magnetic-pole members; and anon-magnetic conductor electrically connecting the semiconductor deviceand the magnetic-pole members in common to one of a low electricpotential side and a high electric potential side of a power supply ofthe semiconductor device.